This invention is generally directed to a novel fabricated tube construction and a process for making the same. More particularly, the invention contemplates a tube construction having a novel shoulder that when joined to a sleeve eliminates the leakage problem which occurs with prior art tube constructions.
Fabricated tubes and processes of forming the same are known in the art. In prior art designs, the manufacture of the tube is essentially as described hereinafter. Initially, a sleeve or cylinder is formed out of a stock material by slightly overlapping the ends of the stock material to form a lap seam. A weld or heat seal is effected along the entire length of the overlapping lap seam. The stock material may be laminated and may have multiple layers and an inner foil lining. Next, the resulting cylinder from the stock are cut to a desired length to form individual sleeves. Thereafter, a neck member including a shoulder, to which the sleeve is to be affixed, is positioned on a mandrel. The sleeve is slid over the mandrel until an end portion of the sleeve is brought up into proximity with a mounting portion of the neck shoulder. Subsequently, with the neck shoulder and sleeve on the mandrel, hot air is applied to the mounting portion of the shoulder and the end portion of the sleeve to soften both components. Next, a die, which includes a radio frequency welder, is brought into engagement about the mounting portion of the shoulder for 360.degree. and through the use of radio frequencies, welds the end portion of the sleeve to the mounting portion of the shoulder thereby producing a slight reforming of the end portion of the sleeve so that it conforms to the radius portion of the shoulder. A cap is then put onto the shoulder and the open end of the sleeve is used to fill the tube. After the sleeve is filled with the desired contents, the open end of the sleeve is sealed to complete the process.
With this prior art design, there is a problem of leakage at the point of the overlapping lap seam of the sleeve at the location of welding to the neck shoulder. Leaks most often occur at the void created at the place where the longitudinal lap seam inner layer spaces the overlapping outer layer away from the shoulder because of the inner layer's thickness. It can be appreciated that at this point, a double layer exists and the area at which the outer portion of the sleeve overlaps the inner portion of the sleeve would not always attain a proper, desired seal. Leakage is particularly prominent with three layer laminates having center layers of aluminum or high temperature film stocks.
In prior art tube constructions, the neck member shoulder surface to which the sleeves are heat sealed are smooth and continuous. The heat sealing technique therefore requires that a great deal of heat from a heat die be conducted through the sleeve into the shoulder to fuse both the shoulder and the sleeve together. Often, process parameters and cosmetic issues dictated less than optimum temperature or duration resulting in failure to close the void created by the seam, and thus, leakage results.
The present invention provides a novel tube construction and a process of making the same which eliminates the leakage problem found in prior art tube constructions. Other features and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings.